Multi-domain GFP-related proteins reported with a structure never seen before in nature

The 2008 Nobel prize was awarded for the discovery and development of the green fluorescent protein (GFP). Since these initial discoveries almost 200 GFP-like Fluorescent proteins (FPs) have been described. FPs have become indispensable in biomedical and basic research as a genetically encoded fluorescent label due to the unique ability of the protein family to synthesize light-emitting chromophores autocatalytically from their own three amino acid residues situated near the center of the FP globule.

A team from Austin, Texas have reported two new proteins displaying primary structures never before encountered in natural FPs in a recently published PPS article. The proteins consist of multiple GFP-like domains repeated within the same polypeptide chain. A two-domain green FP (abeGFP) and a four-domain orange-fluorescent FP (Ember) were isolated from the siphonophore Abylopsis eschscholtzii and an unidentified juvenile jellyfish (order Anthoathecata), respectively.

There has never been any wild-type GFP-related proteins found which contain multiple GFP-like domains within a single polypeptide chain. This paper describes two such proteins and explores possible relationships between individual domains within the four-domain orange-red protein from the anthoathecate jellyfish.

The results reveal a previously unrecognized direction in which natural FPs have diversified, suggesting new avenues to look for FPs with novel and potentially useful features.

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